Imperiled by Volcanic Eruptions, Iceland Scoops Up Answers From the Deep

Iceland is a citadel built from volcanic fire. Its residents are familiar with their country’s frequent volcanic eruptions, most of which are more beautiful than bothersome. But in 2021, the nation was left awe-struck when part of a long-dormant corner of the island burst into magmatic flames, starting a fire that could burn for decades to come.

The first eruption came as a shock. But today, lava regularly snaking across the landscape is the new normal. “This was so strange at the beginning,” said Rebekka Hlin Runarsdottir, a geologist and technician at the University of Iceland. “And now, we’re just living in this reality.”

It’s been 800 years since the southwestern Reykjanes Peninsula was host to active streams of lava. Hoping to find out why volcanism has re-emerged there, scientists are snatching samples of molten rock whenever it bleeds out of the crust.

Collecting lava is a peculiar endeavor. Despite it requiring dealing with precariously hot matter exuding from Earth’s innards, it is not a high-tech endeavor.

The workhorse of lava harvesters is usually the humble shovel. To get a decent sample, scientists jab these gardening tools into the syrupy substance. Doing so feels weird, because lava “is not a normal liquid. It’s more viscous,” said Alberto Caracciolo, a volcanologist and geochemist at the University of Iceland. “It’s kind of similar to honey — or maybe more like a marshmallowlike consistency.”

Then, the incandescent fluid goes into “a random bucket,” filled with water to quench the lava and preserve its revelatory chemical compounds, Dr. Caracciolo said. After that, it’s rushed to the laboratory.

A goal of all this lava sampling is to keep people out of harm’s way. The peninsula’s eruptions aren’t coming from preexisting volcanoes, but from stealthier fissures capable of appearing wherever they like. And other ancient volcanic scars all over Iceland suggest much of Reykjanes is potentially at risk.

The earliest outbursts started in uninhabited valleys next to a mountain named Fagradalsfjall. But since late 2023, the fissures appeared in Svartsengi, which contains a major geothermal power plant and the town of Grindavik. The latest eruption began on Aug. 22, with burnt-orange lava fountaining out of a new 2.5-mile-long crevice.

As shifting magma has caused the ground above to inflate, deflate, tremble and convulse, scientists have tracked its subterranean migration with remarkable precision. Consequently, the authorities have managed to get everyone to safety before each new eruption began, and have built ad hoc walls to deflect the lava away from infrastructure.

But other questions remain unanswered. Why has Fagradalsfjall given the limelight to Svartsengi? Each is a stone’s throw from the other, so “are these systems connected at depth, or not?” Dr. Caracciolo said. Is Fagradalsfjall going to make a comeback? And will other fissure networks awaken across the peninsula, including those close to Reykjavik, the capital city?

The scientists hope that there are clues in the chemistry of the lava they collected. Lava isn’t a homogeneous fluid, but a soup of trapped gases, liquids and iridescent crystals that preserve a record of its genesis within, and journey through, the labyrinth below. By studying the peninsula’s recent past, researchers hope to open a window into its eruptive future.

When a new eruption begins, scientists like Dr. Caracciolo, dressed head-to-toe in heat-resistant gear, rush to the scene and scoop up as much lava as they can carry. Ms. Runarsdottir is one of the researchers tasked with preparing these gathered samples for forensic examination.

Some samples are placed in simple mounts — resin-covered cubes that expose just the surface to geochemists. These are used for quick-look analyses that help researchers answer: Has the general chemistry of the lava changed since the last eruption? Is this business as usual, or is there something glaringly different?

Other samples are made into thin sections — slices of resin-enveloped rock — that showcase the lava’s glassy, kaleidoscopic innards. “I take days making a good thin section,” Ms. Runarsdottir said. These are used to track intricate shifts in the peninsula’s volcanism. Telltale minerals, fluids, textures and hues in those crystalline prisons offer hints. Has the composition changed? Is the magma becoming gloopier, perhaps a little explosive? Or is it becoming runnier, allowing it to speed across the landscape?

Ms. Runarsdottir used to create her crystalline slices in tranquil conditions. That was upended by the first Fagradalsfjall outburst in 2021.

When a sample was rushed to her base by helicopter, Ms. Runarsdottir had to hastily prepare it while everyone in the lab watched. “I was like: OK, don’t mess up, don’t mess up.” The novelty of the situation was stressful, but the thrill of discovery proved exhilarating. “That was really fun to experience, this unknown,” she said.

That urgency still exists. “Everyone is just so excited to know what’s going on,” she said. But like many of her colleagues, she has become accustomed to the periodic pyrotechnics. “It’s a routine now. We’re just waiting for the next one.”

The samples have revealed that the peninsula’s two active fissure systems have similarities in their chemical makeup, suggesting they were both cooked in the same deep geologic oven.

Despite a shared geologic origin, the two volcanic systems are distinct. Fagradalsfjall’s eruptions tapped molten rock that shot straight up from the boundary between the crust and the more malleable mantle below.

Conversely, in the middle of the crust below Svartsengi, there are interconnected magmatic caches, each featuring a novel chemical concoction. “It’s not a single magma chamber, but something more complicated and dynamic,” Dr. Caracciolo said. Sometimes, these eruptions are fueled by a single cache. At other times, multiple caches let loose simultaneously, pouring a complex mélange onto the wintry earth.

Volcanologists are only just starting to understand what’s going on beneath Reykjanes — and the magma’s not making it easy. “Each eruption is showing us something different,” Dr. Caracciolo said. All they can do is chase that lava around the peninsula, shovel and bucket in hand, while more layers of vermilion paint are added to this ever-changing castle rising above the sea.